leetcode

0645.cpp (414B)

 class Solution {
   public:
     vector<int> findErrorNums(vector<int> &nums) const {
         const int n = size(nums);
         int dbl = 0, sum = 0;
         for (int i = 0; i < n; i++) {
             const int num = abs(nums[i]);
             if (nums[num - 1] < 0) dbl = num;
             nums[num - 1] = -nums[num - 1];
             sum += num;
         }
         return {dbl, n * (n + 1) / 2 - (sum - dbl)};
     }
 };